The entire disclosure of Japanese Patent Application No. 9-198635 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to an image processing method for correcting the influences of defects such as dust, scratches, fingerprints, and the like present on a transparent original upon reading image information of the transparent original, an image processing apparatus for executing the image processing method, and a storage medium for computer-readably storing a program for correcting the influences of defects.
2. Related Background Art
An image processing apparatus for reading image information of a transparent original is normally constituted by a host computer such as a so-called personal computer, or the like, and an image reader as an input device of the host computer. The image reader comprises an illumination means for illuminating a film original as a transparent original such as a negative film, reversal film, elongated film, or the like, a moving means for moving the film original, an image reading means for reading an image on the film original by receiving light transmitted through the film original, and outputting an image signal, and an image processing means for calculating data of the image read by the image reading means. The image reader reads an image on a film original on the basis of a command from the host computer, and outputs the read image data to the host computer.
Color image reading is normally done by switching three colors, i.e., red (R), green (G), and blue (B). However, when defects such as dust, scratches, fingerprints, and the like are present on a film original, these defects appear as black points (in case of a positive film) or white points (in case of a negative film) on the read image, thus lowering the image quality.
To solve such problem, a technique for detecting defects such as dust, scratches, fingerprints, and the like using the properties of infrared light and correcting the influences of defects has been proposed (e.g., U.S. Pat. No. 5,266,805). This patent discloses the following technique. That is, when the infrared ray energy intensity detected at a given timing is larger than a predetermined threshold value, the visible ray energy intensity is increased to a level that can cancel the infrared ray energy intensity, and when the detected infrared ray energy intensity is equal to or lower than the predetermined threshold value, the visible ray energy intensity is corrected by interpolation, thereby correcting the influences of defects.
However, the above patent discloses only the concept of the technique for correcting the influences of defects using infrared rays, and does not give any clear description about how to compute the acquired data associated with defects so as to acquire correction data. Hence, the disclosure of the above patent does not enable acquisition of an image free from the influences of defects.
It is an object of the present invention to provide an image processing method that can surely acquire an image free from the influences of defects on a transparent original, an image processing apparatus for executing the image processing method, and a storage medium for computer-readably storing a program for correcting the influences of defects.
An image processing method according to the basic mode of the present invention comprises the steps of resolving the color of an image on a transmissive substrate or original to extract an infrared component (i.e., providing an infrared light component transmitted by a transparent original), detecting the level of the infrared component, detecting a defect infrared component level at a defect position on the transparent original where the infrared component level becomes lower than a first infrared level, obtaining a correction factor by calculating (first infrared component level)/(defect infrared component level) on the basis of the first infrared component level and defect infrared component level, resolving the color of the image on the transparent original to extract a visible component, detecting a visible component level of the visible component, and calculating a corrected visible component level by multiplying a defect visible component level at the defect position on the transparent original by the correction factor.
Noting that the attenuation amount of the transmissive level of the infrared component accurately represents the degree of defects, this method calculates the correction factor as the ratio between the infrared component level (first infrared component level) obtained without any defects and the defect infrared component level at the defect position, and multiplies the visible component level at that defect position by the correction factor. Therefore, since correction can be attained in correspondence with the attenuation amount, an image can be reproduced more appropriately than the conventional method.
In order to make this image processing method properly function, the visible component at the defect position must include recoverable image information. Hence, in one mode of the present invention, a threshold value as a second infrared component level is used as a reference infrared component level, and when the degree of defects is not too serious and image information can be directly recovered, the correction factor is multiplied. In this way, an image can be reproduced more appropriately.
In the image processing method according to one mode of the present invention, when the degree of defects is serious and the infrared component level is smaller than the second infrared component level component, i.e., image information cannot be directly recovered, a visible component level at the defect position is generated using visible component levels around the detected defect position. Hence, even at a position where the attenuation amount due to defects is large, an image which suffers less influences of defects can be obtained.
In the image processing method of the present invention, the first infrared component level can use a maximum value of the detected infrared component levels. In this case, even when the infrared component level varies in each detection, the influences of such variations can be reduced, thus reducing the influences of defects with high reproducibility.
In the image processing method according to one mode of the present invention, the infrared component is extracted by optically resolving the color of the image on the transparent original to extract an infrared component, the infrared component level is detected by imaging infrared light corresponding to the extracted infrared component on photoelectric conversion means by an imaging optical system, and making the photoelectric conversion means output an infrared component signal, the visible component is extracted by optically resolving the color of the image on the transparent original to extract a visible component, the visible component level is detected by imaging visible light corresponding to the extracted visible component on the photoelectric conversion means by the imaging optical system, and making the photoelectric conversion means output a visible component signal, and the method further comprises the step of performing registrational error correction for correcting a registrational error between the infrared component signal and visible component signal due to different imaging positions of the infrared light coming from the transparent original and the visible light coming from the transparent original, that are caused by characteristics of the imaging optical system. With this method, any influences of the registrational error between the focused positions of infrared light and visible light caused by the characteristics of the imaging optical system can be corrected. As a consequence, the size of the infrared component signal region corresponding to defects becomes nearly equal to that of the visible component signal region corresponding to defects. Hence, regions that need not be corrected can be prevented from being corrected.
In this method, it is more preferable that the following arrangement be adopted. That is, the registrational error correction is attained by: setting at least one of the transparent original and the photoelectric conversion means at a position where an image of the transparent original corresponding to the extracted infrared component is to be imaged on the photoelectric conversion means by the imaging optical system when the infrared component is to be extracted; and setting at least one of the transparent original and the photoelectric conversion means at a position where an image of the transparent original corresponding to the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system when the visible component is to be extracted. In this case, registrational error correction is done using a mechanical mechanism. Since the registrational error is optically corrected, registrational error correction that can minimize deterioration of image quality as compared to the one based on data processing such as mathematical operation can be realized.
In this method, it is more preferable that the following arrangement be adopted. That is, the method further comprises the steps of: relatively moving at least one of the transparent original and the photoelectric conversion means to a first sub-scan position; setting at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; extracting said one of the infrared component and the visible component; setting at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to the other of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; extracting said other of the infrared component and the visible component; relatively moving at least one of the transparent original and the photoelectric conversion means to a second sub-scan position; extracting said other of the infrared component and the visible component; setting at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to said one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; and extracting said one of the infrared component and the visible component. In this case, since the number of times of movement of the transparent original or photoelectric conversion means can be reduced, image processing can be done within a short period of time.
Alternatively, it is more preferable that the following arrangement be adopted. That is, the method further comprises the steps of: relatively moving at least one of the transparent original and the photoelectric conversion means to a first sub-scan position; setting at least one of the transparent original and the photoelectric conversion means at a first imaging position where an image corresponding to one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; extracting said one of the infrared component and the visible component; setting at least one of the transparent original and the photoelectric conversion means at a second imaging position where an image corresponding to the other of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; extracting said other of the infrared component and the visible component; relatively moving at least one of the transparent original and the photoelectric conversion means to a second sub-scan position; setting at least one of the transparent original and the photoelectric conversion means at the first imaging position; extracting said one of the infrared component and the visible component; setting at least one of the transparent original and the photoelectric conversion means at the second imaging position; and extracting said other of the infrared component and the visible component. In this case, at least one of the transparent original and photoelectric conversion means is moved in an identical direction to attain imaging. Therefore, high alignment precision can be assured independently of the characteristics of the mechanism for moving at least one of the transparent original and photoelectric conversion means in the imaging direction.
In this method, it is more preferable that the following arrangement be adopted. That is, the method further comprises, after the step of relatively moving at least one of the transparent original and the photoelectric conversion means to the second imaging position and before the step of setting at least one of the transparent original and the photoelectric conversion means at the first imaging position, the step of: setting at least one of the transparent original and the photoelectric conversion means at a position opposite to the second imaging position with respect to the first imaging position. In this case, irrespective of the first and second imaging positions, high alignment precision can be assured independently of the characteristics of the mechanism for moving at least one of the transparent original and photoelectric conversion means in the imaging direction.
Some examples of mechanical registrational error correction have been described but correction may also be attained by a calculation or mathematical operation. For example, the registrational error correction is attained by performing a correction calculation of one of the defect infrared component level and the defect visible component level so as to match a distribution size of the defect infrared component level with a distribution size of the defect visible component level.
In this case, the mechanical mechanism for registrational error correction can be omitted.
In the above-mentioned image processing method of the basic mode of the present invention, it is more preferable that the following arrangement be adopted. More specifically, the method further comprises the steps of: specifying a position in the visible component corresponding to the defect position on the basis of the defect infrared component level and the visible component level; and multiplying the defect visible component level corresponding to the specified position by the correction factor. According to this method, any positional registrational error between the infrared component signal region corresponding to defects and visible component signal region corresponding to defects can be corrected. Hence, regions that need not be corrected can be prevented from being corrected.
In the image processing method of the basic mode, it is more preferable that the following arrangement be adopted. More specifically, the method further comprises, after the step of multiplying the correction factor, the step of: modifying gradation of the corrected visible component level. That is, when gradation correction is executed first, the correction factor must be multiplied taking the gradation correction performed into consideration, thus complicating the processing. However, with this method, such problem can be avoided.
An image processing method according to one mode of the present invention comprises the steps of: optically resolving a color of an image on a transparent original to extract an infrared component; imaging infrared light corresponding to the extracted infrared component on photoelectric conversion means by an imaging optical system, and making the photoelectric conversion means output an infrared component signal; detecting defect position information of the transparent original where a level of the infrared component is lower than a first infrared level; optically resolving the color of the image on a transparent original to extract a visible component; imaging visible light corresponding to the extracted visible component on the photoelectric conversion means by the imaging optical system, and making the photoelectric conversion means output a visible component signal; detecting a visible component level of the visible component signal; performing registrational error correction for correcting a registrational error between the infrared component signal and visible component signal due to different imaging positions of the infrared light and the visible light, that are caused by characteristics of the imaging optical system; and correcting the visible component level on the basis of the registrational error correction. With this image processing method, any influences of the registrational error between the focal points of infrared light and visible light caused by the characteristics of the imaging optical system can be corrected. As a consequence, the size of the infrared component signal region corresponding to defects becomes nearly equal to that of the visible component signal region corresponding to defects. Hence, regions that need not be corrected can be prevented from being corrected.
An image processing method according to another mode of the present invention comprises the steps of: resolving a color of an image on a transparent original to extract an infrared component; detecting levels of the infrared component for a plurality of pixels; detecting a defect infrared component level at a defect position on the transparent original, where the infrared component level is lower than a first infrared level; resolving the color of the image on a transparent original to extract a visible component; detecting visible component levels of the visible component for a plurality of pixels; and specifying a pixel corresponding to the defect position associated with the visible component on the basis of the defect infrared component level and the visible component level.
An image processing apparatus according to one mode of the present invention comprises: infrared component extraction means for resolving a color of an image on a transparent original to extract an infrared component; infrared component detection means for detecting a level of the infrared component; defect infrared component detection means for detecting a defect infrared component level at a defect position on the transparent original where the infrared component level becomes lower than a first infrared level; correction factor calculation means for obtaining a correction factor by calculating (first infrared component level)/(defect infrared component level) on the basis of the first infrared component level and defect infrared component level; visible component extraction means for resolving the color of the image on the transparent original to extract a visible component; visible component detection means for detecting a visible component level of the visible component; and multiplication means for calculating a corrected visible component level by multiplying a defect visible component level at the defect position on the transparent original by the correction factor.
An image processing apparatus according to another mode of the present invention comprises: an infrared light pass filter for optically resolving a color of an image on a transparent original to extract an infrared component; first photoelectric conversion means for photoelectrically converting infrared light and outputting an infrared component signal; defect position detection means for detecting a position of the infrared component signal where an infrared component level is lower than a first infrared level, and outputting defect position information; a visible light pass filter for optically resolving the color of the image on a transparent original to extract a visible component; second photoelectric conversion means for photoelectrically converting visible light and outputting a visible component signal; an imaging optical system for imaging one of infrared light corresponding to the extracted infrared component and visible light component corresponding to the extracted visible light component on a corresponding one of the first and second photoelectric conversion means; and registrational error correction means for correcting a registrational error between the infrared component signal and visible component signal due to different imaging positions of the infrared light and the visible light, that are caused by characteristics of the imaging optical system. This image processing apparatus can correct any influences of the registrational error between the focal points of infrared light and visible light caused by the characteristics of the imaging optical system. As a consequence, the size of the infrared component signal region corresponding to defects becomes nearly equal to that of the visible component signal region corresponding to defects. Hence, regions that need not be corrected can be prevented from being corrected.
An image processing apparatus according to still another mode of the present invention comprises: an infrared light pass filter for optically resolving a color of an image on a transparent original to extract an infrared component; infrared component detection means for dividing the infrared component into a plurality of pixels, and detecting infrared component levels of the pixels; defect infrared component detection means for detecting a defect infrared component level of a pixel at a defect position on the transparent original, where the infrared component level is lower than a first infrared level; a visible light pass filter for optically resolving the color of the image on a transparent original to extract a visible component; visible component detection means for detecting visible component levels of the visible component from a plurality of pixels; and defect position specifying means for specifying a position of the visible component corresponding to the defect position on the basis of the defect infrared component level and the visible component level.
A storage medium which stores a control process of an image processing apparatus according to one mode of the present invention is a storage medium which computer-readably stores a control process of image generation by an image processing apparatus having infrared component extraction means for resolving a color of an image on a transparent original to extract an infrared component, defect infrared component detection means for detecting a defect infrared component level at a defect position on the transparent original where the infrared component level becomes lower than a first infrared level, visible component extraction means for resolving the color of the image on the transparent original to extract a visible component, and visible component detection means for detecting a visible component level of the extracted visible component, the control process comprising the steps of: detecting a level of the extracted infrared component; obtaining a correction factor by calculating (first infrared component level)/(defect infrared component level) on the basis of the first infrared component level and defect infrared component level; and calculating a corrected visible component level by multiplying a defect visible component level at the defect position on the transparent original by the correction factor.
A storage medium which stores a control process of an image processing apparatus according to another mode of the present invention is a storage medium which computer-readably stores a control process of image generation by an image processing apparatus having infrared component extraction means for resolving a color of an image on a transparent original to extract an infrared component, visible component extraction means for resolving the color of the image on the transparent original to extract a visible component, photoelectric conversion means for scanning the transparent original in a main scan direction, and converting light transmitted through the transparent original into an electrical signal, and moving means for relatively moving at least one of the transparent original and the photoelectric conversion means in a sub-scan direction as a direction perpendicular to the main scan direction, the control process comprising the steps of: controlling the moving means to relatively move at least one of the transparent original and the photoelectric conversion means to a first sub-scan position; controlling the moving means to set at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by an imaging optical system; controlling one of the infrared component extraction means and the visible component extraction means to perform component extraction; controlling, after one of the infrared component and the visible component is extracted, the moving means to set at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to the other of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; controlling the other of the infrared component extraction means and the visible component extraction means to perform component extraction; controlling the moving means to relatively move at least one of the transparent original and the photoelectric conversion means to a second sub-scan position; controlling, after the other of the infrared component and the visible component is extracted, the moving means to set at least one of the transparent original and the photoelectric conversion means at a position where an image corresponding to the one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; and controlling the one of the infrared component extraction means and the visible component extraction means to perform component extraction.
A storage medium which stores a control process of an image processing apparatus according to still another mode of the present invention is a storage medium which computer-readably stores a control process of image generation by an image processing apparatus having infrared component extraction means for resolving a color of an image on a transparent original to extract an infrared component, visible component extraction means for resolving the color of the image on the transparent original to extract a visible component, photoelectric conversion means for scanning the transparent original in a main scan direction, and converting light transmitted through the transparent original into an electrical signal, and moving means for relatively moving at least one of the transparent original and the photoelectric conversion means in a sub-scan direction as a direction perpendicular to the main scan direction, the control process comprising the steps of: controlling the moving means to relatively move at least one of the transparent original and the photoelectric conversion means to a first sub-scan position; controlling the moving means to set at least one of the transparent original and the photoelectric conversion means at a first imaging position where an image corresponding to one of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by an imaging optical system; controlling one of the infrared component extraction means and the visible component extraction means to perform component extraction; controlling, after one of the infrared component and the visible component is extracted, the moving means to set at least one of the transparent original and the photoelectric conversion means at a second imaging position where an image corresponding to the other of the extracted infrared component and the extracted visible component is to be imaged on the photoelectric conversion means by the imaging optical system; controlling the other of the infrared component extraction means and the visible component extraction means to perform component extraction; controlling the moving means to relatively move at least one of the transparent original and the photoelectric conversion means to a second sub-scan position; controlling the moving means to set at least one of the transparent original and the photoelectric conversion means at the first imaging position; controlling the one of the infrared component extraction means and the visible component extraction means to perform component extraction; controlling, after the one of the infrared component and the visible component is extracted, the moving means to set at least one of the transparent original and the photoelectric conversion means at the second imaging position; and controlling the other of the infrared component extraction means and the visible component extraction means to perform component extraction.
A storage medium which stores a control process of an image processing apparatus according to still another mode of the present invention is a storage medium which computer-readably stores a control process of image generation by an image processing apparatus having an infrared light pass filter for optically resolving a color of an image on a transparent original to extract an infrared component, first photoelectric conversion means for photoelectrically converting infrared light and outputting an infrared component signal, defect position detection means for detecting a position of the infrared component signal where an infrared component level is lower than a first infrared level, and outputting defect position information, a visible light pass filter for optically resolving the color of the image on a transparent original to extract a visible component, second photoelectric conversion means for photoelectrically converting visible light and outputting a visible component signal, and an imaging optical system for imaging one of infrared light corresponding to the extracted infrared component and visible light component corresponding to the extracted visible light component on a corresponding one of the first and second photoelectric conversion means, the control process comprising: a registrational error correction step of correcting a registrational error between the infrared component signal and visible component signal due to different imaging positions of the infrared light and the visible light, that are caused by characteristics of the imaging optical system.